Whether pestilential disease [morbus pestilentialis] arises from an infection of the air.

One inquires further into the sickness of animals. And because the Philosopher says that fish do not suffer pestilential disease, this is why one asks whether pestilential disease arises from an infection of the air.

And it seems not, because if it arose from an infection of the air, then it would appear equally in flyers and in both wild and domestic walkers, since all of these live in air. Aristotle says the opposite.

Moreover, just as the air can be infected, so too can water, as is clear from standing water. If, then, pestilential disease should arise from an infection of the air, for the same reason it should appear in fish from an infection of the water. The Philosopher says the opposite.

To this one must reply that pestilential disease arises especially from an infection of the air, because when infected air is breathed it infects the lungs, which have a loose composition, and, once the lungs have been infected, then the heart is infected. And this is why a sickness of this sort occurs in those that breathe in and out. But the water is not as easily infected, both on account of its saltiness, as with seawater, and on account of its flowing movement, as with flowing fresh water. Now, salt water is capable of cleansing, and so too is running water, and this is why they do not easily endure such infection. But standing water undergoes infection quickly, and this is why fish in standing water die more quickly than others. Thus this disease can occur in fish, although nevertheless less often than in flyers and walkers for the reason already cited.

Moreover, air is infected by the cadavers of dead animals and by other putrefying things, which are more abundant on the ground's surface than in the upper part of the air, and this is why this disease occurs less frequently in birds than in walkers.

Moreover, domestic animals are in a smaller space in large numbers than are wild animals, and this is why the air is infected more by the multiplication of their exhalation. In the same way domestic animals are moister than wild animals, because they are fat, and moisture is the material for corruption and putrefaction, according to Galen. And this is why domestic animals die more quickly from this disease than do wild animals, and this is especially so for sheep and cows because the sheep is a dull animal, as is said in the text, and lives on earthborn things and it does not discriminate well between things that cause or do not cause corruption. The cow, however, has lungs with a very loose composition, and this is why its heart and spirits are more easily infected once it has breathed corrupted air, etc.

In this way a solution is apparent.

On the sicknesses of pigs, dogs, and horses.

One inquires further why scrofula particularly occurs in pigs.

Second, why a flux in them is only cured with difficulty.

Third, why gout of the feet occurs particularly in dogs.

And fourth, why strangury particularly occurs in horses.

And fifth, why a miscarriage occurs in mares when a candle is extinguished and why the same thing occurs in some women.

And sixth, why human saliva infects a toad, as is said in the text.

And seventh, why an arrow, tinged with human saliva, kills the one struck by it more quickly.

To the first question one must reply that pigs have superfluous moisture and weak heat, and this is why they grow fat so quickly and why their superfluous digested moistures are turned back and cannot be well incorporated. Thus these moistures are directed back into the parts that hang down, and, as a result, to the jaws. This is why the flesh or anterior parts of a pig are less healthful than the others, because they are moister as a result of the superfluous humors running through them, because, according to the physicians, flux more commonly occurs in a part that slopes downward. And in a similar way, the backbone is more healthful than the stomach because the moistures flow to the lower parts. Moreover, the front feet are more healthful than the back feet, because they are more engaged in motion and exertion, and for this reason they are more purged of superfluities. Thus a disease like this occurs in pigs owing to the abundance of the moistures because they are gluttonous and cold and have a bad digestion, like phlegmatics.

To the second question one must reply that flux is of three types. One arises from the moistures, and this is called diarrhoea. Another arises from superfluous nutriment, as when food is excreted in the same form as it was received, and this is called lienteria. And a third arises from the blood, and this one is called dysenteria. Thus the saying among the physicians: "Raw [stool means] lienteric; simple [means] diar(rhoea); bloody [means] dysentery." But humors abound in the pig, and this is why, just as it is difficult to remove a pig's proper complexion, so it is difficult to restrain a proper flux if it should occur in the pig, and the Philosopher is referring to this. Nevertheless, it can be cured if wine is poured in through its anus, because then its intestines are quickly restrained as if by a clyster, etc. If, however, it is poured into its mouth, it is converted into chyle before it reaches the intestines, because it may be changed and it does not come under its actuality. And this is why, etc.

To the third question one must reply that the dog is a dry and melancholic animal and especially given to intercourse, and this is why an illness arising from dryness in the extremities afflicts them particularly, and gout is of this type because coition greatly weakens the nerves, according to Avicenna. And, moreover, they are dried out beyond measure because they are very much involved in motion. For excessive dryness corrupts the nerves, according to Galen in On Illness and Accident.[2]

To the fourth question one must reply that the horse very often wants to urinate, although nevertheless it is not allowed to do so by the one mounted on it or riding it, nor does he perceive its desire to urinate. This is why its bladder is bloated, from the retention of the urine, and thus strangury occurs just as it does in humans, and this is why, etc.

To the fifth question one must reply that the womb is a very sensitive member. Therefore, when it senses something unsuitable in the body's lower part, it rises and flees upward, as is apparent in prolapse of the womb [praecipitio matricis], and if it should sense this in the [body's] upper part, it is pressed downward so that it suffers suffocation. And this is why, when it perceives the bad smell of a candle that has been extinguished, the womb is often pressed downward so much that the womb's cotilideons (those things which bind the fetus to the womb just as an apple is tied to a tree) are ruptured, and then a miscarriage occurs. This also occurs in weak women.

To the sixth question one must reply that animals with a ringed body that lack blood and do not breathe have a very loose composition, especially if they do not have lungs, because animals such as this need to have the interior heat tempered by the exterior air, and this is why their bodies are porous, as is evident in bees and wasps. But the human especially abounds with blood, and the toad and animals like it lack blood. Therefore, their natures are contrary, and this is why if a person's saliva especially that of a person who is fasting, because it is better digestedis poured on a toad, it very quickly penetrates the porous parts of the toad to reach the interior and kills it by virtue of its contrariety. Thus, too, smeared-on spit removes morfea.[3] And the same thing happens with salt, because salt is pungent and penetrating. And this is why people sprinkle meat with it, so that it will not putrefy. Therefore, salt, when it is sprinkled on a toad, penetrates to its internal parts in the same way and kills it, because salt cleanses and expels the filthand all the parts of the toad are filthyand to purge the toad of its filth is to kill it, etc.

To the seventh question one must reply that when something is properly ordered it is amicable, but when it is beyond this order it is inimical, as is evident in many examples. For good blood is amicable in the body, but when it is outside the body, it is inimical to it. Thus, if an ox sees its blood outside its body, it incites it to madness, which I once proved before my brethren at Cologne.[4] But saliva is very amicable in a person, because one cannot speak nor can one take in food without saliva to mediate. But if it is outside the body, then it is very hostile toward it, that is, toward the human body. And this is why an arrow that has been tinged with human saliva kills more quickly than does an arrow that has not been tinged with saliva; etc.

[1] Although one is tempted to translate morbus pestilentialis as "plague," the term would likely be misleading, coming before the Black Death or plague of the fourteenth century. On some of the difficulties with terminology, see Jon Arrizabalaga (1994).